When
youtruncate,
you take the base of a word, add an asterisk, and in this way you
search for sources that have any form of the word in them and thus
you expand your search.

For
example, human* will bring up sources with humans,
humane, humanist,
and humanity in them.

Be
aware that truncation can result in "false
hits," sources which contain your search terms
but have nothing to do with your topic. For example, fund* might
bring up sources with fundamental
in them in addition to those with funds,
funding, funders,
and funded in them.
Putting it all Together

For
purposes of this paper, a search using boolean
operators and truncation
would look like this:

marijuana
or hashish
or cannabis
(since pot, grass, and weed are slang words for marijuana, using
them as search terms probably won't bring up any articles in
peer-reviewed journals where the language is formal)andmedic*
or therapeutic
(medic* will bring up sources with medical, medication, medicine,
and medicinal in them) and
legal* ordecriminaliz*
(legal* will bring up results with legalize, legalizes, legalizing
and legalization in them)
(decriminaliz* will bring up sources with decriminalize, decriminalizes,
decriminalizing and decriminalization in them)

Here is what your search string with boolean operators, nesting,
and truncation should look like.

(marijuana
or hashish or cannabis) and (medic* or therapeutic) and (legal*
or decriminaliz*)